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Thread: seeking advice on 402 engine upgrades

  1. #1
    Join Date
    Jun 2007
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    Waaay out West
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    Default seeking advice on 402 engine upgrades

    Aloha I'm beginning to restore my 1931 402 with an engine untouched since before 1954. When I pulled the drain plug and felt around, chunks of nasties was all I could find. The motor idled fine.

    I have heard of either rebabbiting or conversion to shell bearings, cross drilling the crank for improved flow. I'm seeking advice from other 4 owners on what other upgrades are recommended.

    I have Jerry Hatfield's older book on fours and wonder if following his advice is sufficient?

    Mahalo (as you might have guessed, I live on an island with no other 4 owners around)

  2. #2
    Join Date
    Jan 2008
    Posts
    178

    Default 402 engine upgrades

    Modern bearings and cross drilling the crankshaft probably can do no harm. I have 67,000 miles (over 27 years) on my 440 with babbit bearings and no cross drilled crankshaft and still run 40-45 lbs oil pressure with 10W40 oil. I do run an oil filter which probably makes a big difference. I see no problem with using babbit bearings. My crankshaft is hardchromed. I find it to be a very reliable and durable motor.

  3. #3

    Default

    Howdy Chas,

    There're more (confusing) options than ever now for your Four - Carillo rods, offset pin forged pistons with narrow rings, cleavite tri-metal bearings in alloy carriers, etc.. - of which I indulged in nearly all with my 441 knowing then, but even more so now, that it only takes a few well placed updates to enhance the 4 experience. Depending on you riding habits, I'd look at the following:

    Clutch: King/Qua/Kevlar equivelant enabling use of only 8 springs along with an updated throwout bearing. Besides vastly improving operation, this will preserve your clutch fingers.
    Oil Filter: not essential with babbit mains/rods but absolutely indespensible with any alloy bearing conversions. Try to get the one with right angle threaded fittings at the timing cover retained by large gland nuts.
    Crank Drilling: Unlike modern high flow rate oiling systems, yours is pressurized soaker hose with controlled leak points at the mains/rods/cam. Quickly, uniformily and consistently pressuring this network is not only good for your mains but preserves your vulnerable rod bearings - #2 being the one generally to go first with any oiling system problems.
    Pistons: not essential, but in your climate you would benefit from a modern three narrow ring piston utilizing gas expansion technology rather than the friction/heat creating ring tension approach.

    Regarding bearing conversions, ironically, though a very thin layer, modern Clevites use babbit. It is a superb, forgiving bearing material of which my rider 440 still retains the original babbit mains from the factory though I've long since gone to aluminum shell/vertical twin bushed rods. In a main bearing environment, it's hard to beat and being soft/forgiving, you do not need to do anything more exotic to your crank than drill it and ensure it's reasonable smooth on the bearing journals. But, the reciprocating environment with greater compression load variation at the rod journals stresses it a bit and any oiling system/lubricant shortcomings can ruin it in a hurry with the bearing shoulders failing first leading to a loss of oil pressure and then the bearings themselves breaking up. Modern Bearing conversions lend themselves more to 38-42 machines with enclosed valve trains which are better suited to sustained highway speeds than the earlier models, I'd think long about the epense before undertaking that conversion.

    Lastly, regarding oil filters. Many legendary long-lived machines (BMW /2's) do not have them, per se, instead utilizing slingers to centrifuge out the crumbs before the oil enters the rod bearings. We don't have the luxury of centrifuging to remove crumbs, we have to rely on gravity. The main source for metal after a 4 motor has settled down following a rebuild, is the trans and the idea is have them drop out of the oil quickly instead of migrating forward to the oil pickup tube. This is best accomplished by using modern (thinner) multi-weight oils and bonding a magnet to your sump plug to hold the refuse.
    Last edited by PRG; 06-23-2008 at 11:21 AM.

  4. #4
    Join Date
    Jun 2007
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    Waaay out West
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    Talking Aloha Tom & PRG

    Many mahalos to you both,

    I wish the 402 to be able to handle the 20 minutes or so it takes to climb over the volcanoes on our island. The roads go from sea level to 7,000 ft in 10-20 miles or so. In other words the grades will put a load on the motor. I'm skitterish as since it is going to come apart, I want it to reliable for me and its next owner - whom ever it may be.

    Any opinions on cost and whom to ask, besides Max Bubeck?

    Carrillo con rods?, wow, what with the stock bent pushrods its hard to believe they would be needed!

  5. #5

    Default Carillo rods needed? ...likely not

    Howdy Chas,

    Need for Carillo rods?........no sir, they likely are not as I subtly alluded to in my opening statement but will now elaborate on under the heading of confusing number of options as touched on in that post so that others may judge their rebuild plans accordingly. I've had an eye opening experience with this recently.

    These rods and other over the top pieces were decided on back in my late 30's when I initially undertook this 441 rebuild (too exuberantly) 13 years ago. In retrospect, bushed stock (metal gets a little to thin on the rod at the small end) or maybe bushed shell converted Indian vertical twin rods would have been more than adequate as the latter have provided superb service in my 440 ridden extensively in the intervening years for one very specific reason. 38-42 Four engine's performance envelope is defined by one limitation rendering some (expensive) improvements unnecessary - heat dissipation at the exhaust valve/seat.

    Optimize a 4 with slightly raised compression, electronic ignition, more accurate fuel management (Cotten float set lower) enabling tuning leaner for more power with more aggressive ignition settings and with a lightened flywheel you'll have a superbly responsive motor, except for one thing. It's exhaust thermal limit is exceeded at anything over about 75F ambient at highway speeds resulting in detonation and run-on when switched off. Mind you, this situation arises with acceptable oil temps and no signs of soft seizing from piston/cylinder clearance problems - it basically cannot transfer heat and speeding up in the belief more airflow will help only adds to the problem - it's exhaust valve area is too enshrouded in heavy cast iron with too little air flow. A shortcoming the factory addressed with the poorly received upside down Fours then only to revert back to the IOE arrangement - compromising by recessing the plugs rather far and enshrouding the exhaust valve from direct flame propogation by necking down the plug well at the combustion end and aiming it away from the valve.

    The solution, either richen it back up to soften combustion and/or add more exhaust valve clearance for more seated duration and hope for a little more heat transfer. I'll be doing the latter first then richening back while keeping a close watch on my AFR meter. The bottom line? You're dialing back power to nearly its original sedate level so essentially you're rendering some very expensive modifications unnecessary.

    Now, for an engine builder, you may want to contact Robbie Robinson who happens to be in CA somewhat close to you. Contact information is at his site here.

    Good luck with your rebuild.

  6. #6
    Join Date
    Jun 2007
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    Default

    Aloha Peter, thanks for the advice, it is appreciated. About temperature control thru the exhaust system. It has been my experience that there are 'build in flaws' in many early I/O systems, the Chevette is another example.

    I'm not looking for power as much as increased reliability.

    I have a question for you, are you running regular or premium as my experience has been that premium runs a bit cooler?

    Has anyone done a thermal Finite Element Analysis (FEA) to see if any grinding/thinning on the iron head will increase heat transfer without increasing stress?

    Thanks for the heads up on a motor builder.

  7. #7

    Default octane recommendations...fodder for much debate

    Howdy Chas,

    Fuel - debated since the dawn of internal combustion so will pontificate thusly from a purely pedestrian perspective. Text book standpoint: career oil company engineer friend said no effort put into regular grade, they regularly (pun intended) made no attempt to keep from mixing other liquids with regular when making pipeline content changeovers. Market demographics for this blend had low expectations and they didn't disappoint. Lower octanes light off easier with quicker (less controlled) flame propogation - the latter key to Rolley Free's record attempts. He purposely strived to tune for lower grades, takes less of an ignition system - in this case Lucas magneto on a Vin - to light off and has more btu-to-volume content because of lack of non/low flammability compounds designed to control its combustion.

    I've used mid grade only in both my Fours, the 440 for the last 13 years predominantly ridden in hot southern weather and geared very tall (19tooth on 18 inch rims) with a XXL rider aboard which generates high sustained cylinder pressures at relatively low rpm - a scenario inviting detonation. But, its not this condition that'll cause it to rattle, or detonate, rather, hot spots around the exhaust area which cause pre-ignition regardless of where you have your advance set. Which, moving up to high test to alleviate is masking the real problem. Though modern stainless exhaust valves raise the thermal tolerance over original metalurgy, hot spots sufficient to ignite fuel are undesirable in any internal combustion engine. I'd probably not look to slow combustion/flame propogation further by using premium - anything not burnt as the exhaust valve begins to lift heats it even further without the seat to dissipate that heat, ie, like running with ignition retarded which makes your headers glow.

    Early Fours are less robust than the 38-42's but they also have to pull substantially less weight around. You mentioned the benchmark being climbing a sustained grade over a mountain pass. Elevated cylinder pressure from generating max torque and resultant heat is what you're looking to avoid. As the thermal limit can't be mitigated (I'd avoid grinding off anything on your rare pieces) the least exotic but most expedient solution would be shorter gearing, spinning the motor a touch faster while reducing peak loading.

  8. #8

    Default

    Peter,
    regarding the heat around the exhaust valve; when I rebuilt my F head engine, I had a ceramic coating applied to the exhaust valve head and in the port as well. The thinking was that it might help reduce the heat accumulation in this area.
    Alas, I havent run the engine yet. Has anyone else tried this?
    Cheers Steve
    Steve

  9. #9
    Join Date
    Jun 2007
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    Default Mahalo 2 u both & another question

    Being a nuts & bolts engineer by trade, I was wondering if there has been any Finite Element Analysis fluid flow or thermal work done on an F Head? Anyone know?

    And Peter, any thoughts on what oil to use in a mid 60's-80's environment

  10. #10

    Default

    Howdy Chas,

    15-50W, no need to get exotic synthetics - with no oil filter and poor oil control, our motors saturate oil with suspended contaminates long before it breaks down - especially with the latest formulation changes.

    As a flat tappet motor, your focus are oils retaining ZDP/ZDDP to protect against sheer at your cam/lifter interface and your bevel gears, these compounds can still be found in diesel oriented forumulations. May want to take a gander at the article I posted here over at the Virtual Indian board from the Porsche Club magazine which explains this latest concession to emissions which will affect our old motors dramatically.

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